Automatically controlled cooking area ventilating system

ABSTRACT

A cooking area ventilating system which operates automatically through the expedient of an aerosol particle sensor. The system operates automatically in response to aerosol particles or smoke, and has a varying speed for the ventilator fan depending on the concentration of the particles that are to be removed by the ventilating system.

United States Patent Inventor Elmer A. Carlson Richfield, Minn. App].No. 30,738 Filed Apr. 22, 1970 Patented Dec. 7, 1971 Assignee HoneywellInc.

Minneapolis, Minn.

AUTOMATICALLY CONTROLLED COOKING AREA VENTILATING SYSTEM 6 Claims, 3Drawing Figs.

US. Cl

' [56] References Cited UNITED STATES PATENTS 2,726,594 12/1955 Cooperet al. 98/49 3,489,345 l/l970 Moreland 236/9 A 2,339,987 [/1944 Evans98/49 3,207,058 9/l965 Gaylord 98/115 K Primary Examiner Edward J.Michael Attorneys-Lamont B. Koontz and Alfred N. Feldman ABSTRACT: Acooking area ventilating system which operates automatically through theexpedient of an aerosol particle sensor. The system operatesautomatically in response to aerosol particles or smoke, and has avarying speed for the ventilator fan depending on the concentration ofthe particles that are to be removed by the ventilating system.

PATENTED BEE 7 ISYI FIG. 3

ELECTRIC HEATER 24- METAL OX'DE 6| PARTICLE DETECTOR v 4 8| CONTROLKlTCHEN OR RANGE VENT HOOD FAN MOTOR INVliN'I ()IL ELMER A. CARLSON WWWATTORNEY.

AUTOMATICALLY CONTROLLED COOKING AREA VENTILATING SYSTEM BACKGROUND OFTHE INVENTION The use of ventilating systems for kitchens or cookingareas, either in a vent hood or for the general room area, are quitewell known. In the past, the ventilating system has been put intooperation manually depending on the need for ventilation as sensed bythe person working in the cooking area.

SUMMARY OF THE INVENTION The present invention is directed to a systemfor automatically turning on the ventilating fan in a kitchen or rangehood in response to aerosol particles in the air. The term aerosolparticles generally encompasses all types of particles generated duringthe cooking process including smoke unburnt hydrocarbons, etc. Thepresently disclosed system not only operates the ventilating fan inresponse to aerosol particles, but varies the speed of the fan based onthe concentration of these particles.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a representation of a typicalinstallation encompassing the present invention;

FIG. 2 is a schematic circuit diagram of a complete system; and

FIG. 3 is a representation of part of a solid-state aerosol particlesensor means.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. I a conventional kitchenrange vent hood I is disclosed. It is understood that the vent hoodcould in fact be the kitchen itself where no specific hood is providedbut where a ventilating fan is used. The fan and its driving motor areshown at 11 connected by conductors l2 and 13 to the automatic control14 which in turn is energized by conductors l5 and I6 from aconventional source of potential. The automatic control I4 is disclosedin detail in FIG. 2.

In FIG. 2 the conductors I5 and I6 are shown connected to the automaticcontrol 14 which includes a primary winding ofa stepdown transformer 21that has a further winding 22 to provide a low voltage to an aerosoltype of sensor 23. The sensor 23 is a solid-state aerosol particlesensor means of a wellknown type. This sensor will be disclosed in moredetail in connection with FIG. 3, but at the present it is sufficient tounderstand that the solid-state aerosol particle sensor means 23includes a heater 24 that is connected across the secondary transformerwinding 22 so that the sensor means 23 is heated to an elevatedtemperature as compared to room ambient during the normal operation ofthe sensor means 23. The sensor means 23 has a further terminal 25 thathas developed between it and the heater 24 a varying resistance value asa function of the number of aerosol particle particles which are presentin the atmosphere around the sensor means 23. The aerosol particles, asused in the present description, are particles such as unburnthydrocarbons, smoke, etc. and these particles vary or reduce theresistive connection between the heater 24 and the terminal 25 as anincrease in concentrations exists. This variation in the resistancevalue is used for the operation of the balance of the system, as will bedescribed below.

The transformer secondary 22 and sensor means 23 are connected byconductor 26 to conductor I5 so that the line voltage is applied acrossthe sensor means 23 to the terminal 25. Terminal 25 is connected byconductor 30 to a switch 31 which in turn is connected through impedance32 and further impedance 33, in the form of a capacitor, to a currentlimiting inductance 34 which in'turn is connected to conductor 16. Theswitch 31 has two positions, 35 and 36. Position 35 is for automaticoperation wherein the sensor means 23 is connected to impedance means32, 33, and 34. The position 36 is for manual operation and bypasses thesensor means 23 by the insertion of a resistor 37 which is connected byconductor 38 to the supply line 15. It is obvious that when switch 31 isin the position shown, that is connected to terminal 35, the sensormeans 23 is connected in the system. When the switch 31 is connected tothe resistor 37 and conductor 38, the system is in a manual orcontinuously operating mode.

Connected across the sensor means 23 and switch 31 are a group of fixedand variable resistances 40, 41, an and 42 which are used for adjustingthe operating parameters of the system in a conventional fashion.Connected to line 15 is the fan motor 43 which is part of the fan andmotor structure I I of FIG. 1. The fan motor 43 is connected byconductor 44 to a solid-state switch means 45 disclosed as a triac. Thetriac 45 is connected by conductor 46 back to the inductance 34 tocomplete a main current conducting path for the fan motor 43. The gate50 of the solid-state switch means 45 is connected by conductor 51 to avoltage breakdown means 52 disclosed as silicon bilateral switch or adiac. The voltage breakdown means 52 is connected at junction 53 betweenthe impedance 32 and the capacitor 33. The diac 52 and triac 45 are usedin a conventional motor speed control circuit which in itself is wellknown in the art. A pair of capacitors 54 and 55 along with a resistor56 are provided across the triac 45 as a filter, which is also wellknown in the use of the triac 45 for motor speed control purposes.

OPERATION OF FIGURE 2 As soon as the line voltage is applied onconductors l5 and 16 the transformer 21 provides a low voltage to heater24 of the sensor means 23. This heater raises the sensor means 23 intemperature, well above the ordinary ambient, thereby providing a propermode of operation of an oxide type of aerosol sensor as is disclosed inthe present application. After the sensor 23 has stabilized intemperature, the system is ready for operation and in a normalinstallation the sensor would be activated at all times. With linevoltage applied between conductors l6 and 26, a current would flowthrough the sensor means 23, the switch 31, the impedance 32, thecapacitor 33. and the inductor 34. The level of current flow is afunction of the resistance between the terminal 25 and the heater 24.This resistance varies as a function of the aerosol particles present atthe sensor with the resistance decreasing with the particleconcentration increasing. The particle concentration is a function ofthe smoke and unburnt hydrocarbons being generated at the kitchen orrange vent hood 10 of FIG. I. The sensormeans 23 is placed within thekitchen or range vent hood 10. When the particle concentration raises toa selected level the sensor means resistance drops sufficiently low sothat the energy supplied to the capacitor 33 is sufficient to cause thediac 52 to breakdown and conduct through the gate 50 of the triac 45.This conduction causes the traic. 45 to conduct thereby supplyingelectric energy to the fan motor 43. The point in which the breakdown ofthe diac 52 occurs with respect to the applied alternating currentvoltage is a function of the impedance of the system that charges thecapacitor 33. The lower the impedance of the circuit, the earlier withinthe applied half wave of the alternating current the breakdown of thediac 52 occurs thereby supplying more energy to the fan motor 43. It canthus be seen that as the concentration of aerosol particles at thesensor means 23 increases, the speed of the fan motor 43 increases. Thisarrangement automatically compensates for increase in smoke and aerosolparticle concentrationto increase the fan motor speed to clear theundesired combustion products present at kitchen or range vent hood 10.Negative feedback of the control system occurs due to locating thesensor 23 within the intake duct hood 10. Increased fan speed draws moreexcess air to the range thereby diluting the particle concentration. Thediluted signal thereby provides a form of negative feedback to stabilizethe fan speed. The minimum fan speed also provides a continuous sampleof room and range air to the sensor for greater response to the roomconditions.

In the event that it is desired to operate the fan motor 43 for removalof odors or materials that the sensor might not respond to, a manualposition 36 is provided for switch 31. In the manual position 36. theimpedance 37 placed in the charging circuit for the capacitor 33 issufficiently low to cause the fan motor 43 to operate at a predeterminedand fixed speed. A minimum speed is set into the installation by theposition selected for the potentiometer 41 and potentiometer 42.

In FIG. 3 a partial section of a typical solid-state aerosol sensormeans is disclosed. The sensor means 23 includes a glass sensor member60 which is coated by a metal oxide coating 61. A typical metal oxidewould be tin oxide and this metal oxide coating completely encircles orencapsulates the glass 60. Embedded in the metal oxide 61 is an electricheater 24 which raises the temperature of the sensor means 23 when theends of the electric heater 24, disclosed at 62 and 63, are connected tothe transformer secondary 22 of FIG. 2. in FIG. 2 a terminal 25 for themetal oxide of the sensor means 23 was disclosed. This can be any typeof a terminal embedded in the metal oxide 61 of FIG. 1, so that thecomplete circuit can be completed from the terminal 25 to the electricheater 24 of the sensor means 23.

The simple system disclosed in the present application provides forcomplete and automatic control of a kitchen or range vent hood for theremoval of undesired smoke and odors which accompany many types of mealpreparation. The automatic operation provides for the removal ofundesired airborne components without the need of the housewife beingpresent and allows for the automatic removal of odors that occur due toinadvertent spills or the boiling over of foods during preparation. inmany cases, this type of odor generation occurs when the housewife isnot present to turn on the vent fan in time to prevent the odors frombeing distributed throughout the cooking area. The simple automaticcontrol provided allows for continuous automatic monitoring of thecooking operation and the varying speed necessary to clear the generatedaerosol particles at a rate commensurate with their production. Thesimple system disclosed is but one way of carrying out the presentinvention and the applicant wishes to be limited in the scope of hisinvention solely by the scope of the appended claims.

I claim: The embodiments of the invention in which an exclusive propertyor right is claimed are defined as follows:

1. An automatically controlled cooking area ventilating systemincluding: solid-state aerosol particle sensor means mounted in acooking area and having a varying impedance in the presence of varyingconcentrations of aerosol particles; circuit means including said sensormeans and impedance means adapted to be connected to a source of voltageso that a varying voltage is developed across said impedance means withvariations of concentration of aerosol particles at said sensor means;and motor control system means adapted to be connected to ventilatingfan motor with said motor control system means responsive to saidvarying voltage to automatically ventilate said cooking area when apredetermined concentration of aerosol particles are present in saidcooking area.

2. An automatically controlled cooking area ventilating system asdescribed in claim 1 wherein a ventilating hood is mounted above saidcooking area and said sensor means is mounted within said ventilatorhood so that when said ventilating fan motor is operating an air flowthrough said ventilator hood passes over said sensor means.

3. An automatically controlled cooking area ventilating system asdescribed in claim 1 wherein said solid-state aerosol particle sensormeans is a metal oxide type of sensor including heater means with saidheater means operating said sensor at an elevated temperature.

4. An automatically controlled cooking area ventilating system asdescribed in claim I wherein said motor control system means includessolid-state switch means in series circuit with said fan motor; andvoltage breakdown means connecting said solid-state switch means to saidimpedance means to control the current flow in said solid-state switchmeans to vary the speed of said fan motor with the amount of aerosolparticles present at said sensor means.

5. An automatically controlled cooking area ventilating system asdescribed in claim 4 wherein said solid-state switch means is a triacand where said voltage breakdown means is a silicon bilateral switch.

6. An automatically controlled cooking area ventilating system asdescribed in claim 4 wherein said solid-state aerosol particle sensormeans is a metal oxide type of sensor including heater means operated atan elevated temperature by said heater means.

1. An automatically controlled cooking area ventilating systemincluding: solid-state aerosol particle sensor means mounted in acooking area and having a varying impedance in the presence of varyingconcentrations of aerosol particles; circuit means including said sensormeans and impedance means adapted to be connected to a source of voltageso that a varying voltage is developed across said impedance means withvariations of concentration of aerosol particles at said sensor means;and motor control system means adapted to be connected to ventilatingfan motor with said motor control system means responsive to saidvarying voltage to automatically ventilate said cooking area when apredetermined concentration of aerosol Particles are present in saidcooking area.
 2. An automatically controlled cooking area ventilatingsystem as described in claim 1 wherein a ventilating hood is mountedabove said cooking area and said sensor means is mounted within saidventilator hood so that when said ventilating fan motor is operating anair flow through said ventilator hood passes over said sensor means. 3.An automatically controlled cooking area ventilating system as describedin claim 1 wherein said solid-state aerosol particle sensor means is ametal oxide type of sensor including heater means with said heater meansoperating said sensor at an elevated temperature.
 4. An automaticallycontrolled cooking area ventilating system as described in claim 1wherein said motor control system means includes solid-state switchmeans in series circuit with said fan motor; and voltage breakdown meansconnecting said solid-state switch means to said impedance means tocontrol the current flow in said solid-state switch means to vary thespeed of said fan motor with the amount of aerosol particles present atsaid sensor means.
 5. An automatically controlled cooking areaventilating system as described in claim 4 wherein said solid-stateswitch means is a triac and where said voltage breakdown means is asilicon bilateral switch.
 6. An automatically controlled cooking areaventilating system as described in claim 4 wherein said solid-stateaerosol particle sensor means is a metal oxide type of sensor includingheater means operated at an elevated temperature by said heater means.